The broad, long-term objective of the current research is to reduce the prevalence of disordered gambling and co-morbid substance use disorders and related harm in the population, through development of efficacious and cost-effective indicated prevention/early intervention techniques. While many individuals gamble as an occasional form of entertainment, a significant subset of the population experiences substantive harm related to their gambling. Gambling has been described as a behavioral addiction, with considerable neurobiological and symptom similarity to substance use disorders (SUD). Further, disordered gambling is associated with very high rates of alcohol and drug (AOD) use and SUD co-morbidity. Gambling has been conceptualized as a continuum, from no gambling and non-problem gambling, to at-risk gambling, to diagnosable pathological gambling. Disordered gambling (at-risk and pathological) is estimated to affect 3-5% of the U. S. adult population, with higher rates often reported in young adult (college aged) populations. Disordered gambling has been associated with a host of serious consequences for the gambler and society, including financial, legal, social, familial, and work/educational difficulties as well as elevated rates of anxiety, depression, and suicidal ideation and behavior. These findings have lead to an increasing recognition of disordered gambling as a significant public health problem. The current research builds on our prior work on development of indicated prevention approaches for disordered gambling (R21 MH067026). Our findings indicate a brief, personalized feedback intervention (PFI) utilizing graphic feedback and motivational enhancement strategies is efficacious in reducing gambling and related consequences in a vulnerable population (college students) at risk for or already evidencing pathological gambling. Based on these encouraging findings, we propose to evaluate the longer-term efficacy of this approach, and determine relative efficacy of web- and in-person implementation of PFI interventions, for at-risk gamblers with co-morbid SUDs. Specific aims are: 1) Evaluate relative efficacy of in-person vs. web-based PFIs in comparison to assessment only, in reducing gambling behavior, AOD use, and related consequences of at-risk college student gamblers with SUDs. Participants (N=375) screened as at- risk gamblers with SUD will be randomly assigned to one of 3 conditions: a) in-person motivational PFI; b) web-based PFI; or c) repeated assessment comparison group, assessed at post-intervention, 3-, 6-, 12-, and 24-month follow-up. 2) Evaluate choice of intervention, gambling motives, and substance use as moderators of efficacy. 3) Evaluate mediators of intervention efficacy, including perceived descriptive gambling norms, readiness to change, illusions of control, and depth of processing of information.